Shakugan No Shana

Coming home from school one day, he is suddenly caught in a time freeze. From nowhere, a huge monster appears and begins devouring people who have been turned into flames. Just as Yuuji is about to suffer a similar fate, a girl with red eyes and fiery long hair saves him. 

The girl calls herself a Flame Haze who slays “Guze no Tomogara”-- denizens of another realm -- invading the human world. She then proceeds to tell Yuuji that he isn’t human. In fact, he’s a “Torch”, a replacement for the real Yuuji Sakai who no longer exists in this world.... 

However, Yuuji’s more than a Torch; he’s a “Mystes”, and holds a powerful treasure within him that the Tomogara will want for their own. Realising this threat, Yuuji and Shana decide to team up as they prepare for their long and arduous battle against the Guze no Tomogara.